Fluid pump



Dec 19, 1939.

G. A. WAHLMARK FLUID PUMP Filed April 2, v195'/ 2 Sheets-Sheet 1 E M bv Dec. 19, 1939. G. A. WAHLMARK FLUID PUMP Filed April 2, 1937 2 Sheets-Sheet '/llllIll/l/Afl) Patented Dec. 19, 1939 PATENT OFFICE FLUID PUMP Gunnar A. Wahlmark, Rockford, Ill. Application April 2, 1937, Serial YNl). 134,594

9 Claims.

The invention relates generally to a fluid pump and associated control valve device, and more particularly to a discharge control for oil burner pumps.

The principal object of the invention is to provide a new and improved fluid pressure generating and control means for a fluid pressure system operable to initiate discharge of iluid at fullp ressure and volume, and to end discharge with a sharp cut-oil at substantially full pressure and volume.

Another object of the invention is to provide a new and improved fluid pressure generating and control means for a uid pressure system operable to initiate sudden discharge when the fluid flow from the means reaches a maximum.

Yet

another object is to provide a new and improved fluid pressure generating and control means for a fluid pressure system operable to effect sharp cut-oli as soon as flow from the means falls below the maxim Still another object is a valve device for the pump, by-pass the discharge from the pump to provide a pump and the valve operation being designed to until a predetermined pump output is reached, and then immediately to close the Dump displa by-pass and cause the to discharge normally until the volumetric cement of the pump drops below the predetermined value, at which point the valve device is immediately operable to cut off the discharge and resume by-passing of the fluid.

urther object is to provide a control, for having a pressure the operating disand means respondisplacement of the pump for governing 4the building up of pump pressure.

urther object is to provide a control, for

the discharge from -a pump, having a pressure responsive valve governing the operating discharge pressure of the communicating with the discharge in advancev J vto the suction at the pressure of pump, a by-pass passage d valve, and valve means responsive either the intake of the pump or to the by-passed fluid or both,

governing the by-pass passage and operable to close the lay-pass passage as the pump comes up to full displacement, discharge pressure responsive valve thereby to compel normal from the pump under the control of the and to open the bypass with a drop in pump displacement.

Other objects and advantages will become apparen t from the following detailed description,

-shall hereinafter be described in detail controlling the discharge from (Cl. S-42) taken in connection with the accompanying drawings, in which:

Fig. 1 is a longitudinal secton through thev preferred form of the invention at the center line.

Fig. 2 is-a somewhat diagrammatic longitudinal section slightly to one side of the center of the device, with. the pump members rotated 90 in order to show conduits and ports not otherwise clearly visible. l

Fig. 3 is a cross section taken on the line 3--3 of Fig. 1, looking in the direction of the arrows.

Fig. 4 is a fragmentary central sectional view of thevvalve device showing the position occupied 1,;

l by the parts when the pump is running.

Fig. 5 is a fragmentary section showing the return outlet and an internal return leading to the screen chamber.

While there is illustrated in the drawings and a preferred form of the invention, it is to be understood that the invention is not limited to the particularconstruction and arrangement shown, it being contemplated that various changes may be made by those skilled in the art without departing from the spirit and scope of the invention as expressed in the appended claims.

In the exemplary form of the invention shown in the drawings, there is presented a fuel unit embodying a pump and a control therefor-including a compound valve and by-pass system so arranged that,` in operation, when fluid is drawn into the pump, it is discharged to the compound `valve and by-pass system and in the period during which the pump is picking up speed the huid so discharged is connected through a by-pass valve back to the pump or the source. By means ofan increase in suction, created at the intake of the pump as it picks up speed, or by means of an increase in pressure of the'by-passed fluid 40 due to increased displacement of the pump, or by means of both, the by-pass valve is drawn to a closed position forming a pocket within the compound valve device. Immediately upon closure of the by-pass, pressure is built up within this valve device and reacts on another lower valve, controlling discharge from the pump, causing it to. snap it open, thereby releasing fluid to the burner nozzle at the full built up pressure and volume of the pum Subsequently, upon shutting oif the pump, the vacuum previously created is brokenv andthe pressure reduced so that a spring working in a direction opposed to thole forces opens the by-pass valve and causes a reduction of pressure within the valve device 55.

lto the valve body Aand 2I fluid is conducted tlr rotary pump 2.

which in turn causes the lower valve to snap shut and abruptly cut oi the direct discharge of fluid before there is any apparent drop in pressure.

To accomplishthe purposes and the operation abov'e described, a unitary mechanism, constituting the invention is provided consisting of a pump base I to which is secured a housing 5 having a cover I0. pump 2 of the rotary type is mounted on the base and driven by a shaft 3 journaled in the base, while in the housing there is an inlet I 5 for the supply of uid and an outlet 65 for discharge from the mechanism to a burner nozzle. The housing has a large inner cylindrical chamber forming a strainer cup 6 at the bottom of which is supported a compound valve structure consisting of a lower valve 35 and an y upper valve 44, each mounted on a diaphragm. Above the upper valve is a sealed chamber 6D connected with the pump intake and above the sealed chamber, separate and distinct from it, is a screen forming an inner chamber I1. Fluid courses from the inlet I5 into the screen chamber I1, thence to the pump 2 from which it is discharged to the compound valve device. During certain periods the fluid is returned through a by-pass to the pump and lduring other periods it is forced through the lower valve to the outlet 65.

As shown in the drawings, the structure consists generally ofthe pump base I upon whichthe rotary pump 2 is mounted and connected to a drive shaft 3 as above described. Secured to -the pump base by means of bolts 4 is the housing 5 containing the compound vvalve mechanism herein referred to. Chamber 6 lies concentrically Within the housing 5, and at the bottom of the chamber a valve body- 1 is secured to the housing in a conventional manner by screws or other means not shown. A cap 8 is similarly secured 1. Also within the chamber 6 is a double screen lter 9 which is held in place ,by the cover I Il of the housing,-secured thereto ,by means of cap screws II.

Fluid, such as fuel oil, enters the device at the inlet port I5 (see Fig. 1) and is conducted througha passage I6 into the inner chamber I1 formed by the double screen filter. From the inner chamber I1, iluid passes outward through the mesh of the screen into an annular space I8 surrounding the double screen iilter and thence outward through passages I9 and 2| to the pump (see Fig. 2). Within the passage I9 is a restriction 20 for a purpose which will be subsequently`described. From the passages I9 to an inlet port 22 of 'I'he .rotary pump, which may be of the type disclosed either in my patent application Serial No. 675,218, ledJune 10, 1933, or in my patent application Serial No. 14,017, led April 1, 1935, is shown more clearly in cross section in Fig. 3 wherethe elongated inlet port 22 appears at the right. 'I'he pump is composed of a toothed rotor 23, which is splined to the shaft 3, and meshes with an internally toothed annular ring 24 positioned eccentrically with the rotor. A crescent member 25 fills the more or less crescent-shaped space between the rotor and the annular ring. For forming the body of the Dump itself an annular'casing 26 is provided which forms a cylindrical interior 21, and a plate 28 constitutinga closurefor the cylindrical interior is positioned on the casing. Screws 29 shown in :section in Fig. 3' secure the plate 23 and thepump casing 26 to the pump base I.

After iuid is drawn into the pump at the inlet port 22, it is discharged through an elongated outlet 30 shown on the left side in Figi. 3, after being carried around in the pockets between the teeth of the rotor and the annular ring. From the outlet port 30 (see Fig. 2), uid

is conducted through a conduit 3| in the pump base I and through a continuation 32 of the conduit situated in the lower part of the housing 5 from which it passes upward, through an aperture in the diaphragm at the clamped edge thereof, and continues on to a conduit 33. From the conduit 33 in the valve body 1, the fluid iiows into anannular chamber 34 formed upon the inside of the valve body.

Allaminated diaphragm 35, consisting preferably of an oil-proof fabric, is secured between a shoulder 35 of the housing 5 and the valve body 1 and forms one side of the annular chamber 34. A disk valve 36, which may be of leather, is secured to the diaphragm 35 together with a cupshaped cylindrical member 31 attached on the opposite side to lend rigidity to the valve element thus assembled. After entering the chamber 34, following initiation of pump operation, the fluid flows immediately through an aperture '38* (see Fig. 1), a lateral conduit 39 and thence upwardly through a passage or conduit 40. The conduit 40 is formed in a plug-like cylindrical member 4I which is securely sealed concentrically within the valve body 1. About midway of the plug-like member, an annular groove 42 is cut ball 39' of slightly larger the passage during the course of manufacture.

Adjacent the annular groove 42 is positioned a crrresponding annular groove 43 which is cut in the inner surface of a sliding sleeve valve 44. A conduit 45 extends longitudinally from the annular groove 43 and forms a connection from the conduit 40 to an annular chamber 46 formed on the upper side of the valve body 1. nated annular diaphragm 41, preferably of oilproof fabric, together with the sleeve Valve 44, forms an upper wall for the annular chamber v 46. At its inner periphery the diaphragm 41 is clamped between a flange between the valve body 1 sleeve valve is depressed into the position shown in Fig. 1 by means of a spring 49 capped by a washer which is adjusted in place by means of a screw 5I fitting into a semi-spherical depression 52 in the top of the washer. The uid after arriving in the annular chamber 46 passes outwardly through a by-pass conduit or passage 53 into a chamber 54 formed within the left side of the housing 5 which surrounds the pump.

-In the set-up shown,

the passage I6 which, as has been previously described, leads from the inlet port I5 to the screen chamber. The passage .56, furthermore, is threaded so that it can be closed by a plug for an alternate "set-up. Should `it be desired to conduct the excess fluid back to the supply tank, a large plug 51 can be removed from a threaded return port 58 and a small plug inserted in the passage 56 to seal it ol. Then a pipe or tube leading to the supply tank can be connected to the threaded return port 58. Another connection .for the partial recirculation of oil is a screened opening 59 shown in the plate 26 located at the lower part of the chamber 54. When there is fluid in the chamber, as is usually the case, the uid may flow by gravity into pockets between the teeth of the rotating pump members should they be not quite full or the fluid may act as a primer for the pump at the initiation of operation.

When the pump is started at slow speed, the course of fluid through the valve device is from the pump around through the described circuit and back to the chamber 54, and the fluid contlnues to pursue that course until the pump reaches full speed. At full speed means to be presently described become eiective to change the course.

As shown herein, the means effective to change the course of the fluid is responsive to two forces which vary with the displacement of the pump, namely, Athe suction at. the inlet of the pump andl the pressure of the by-passed fluid, though either might be employed alone. To that end a sealed chamber 66 is formed by the cap 8 over the upper -side of the upper diaphragm 41, around the `flow to cause a space occupied by the spring 49. A suction duct 6l (see Fig. 2) leads from the sealed chamber 66 through apertures made in the clamped portion of the diaphragm back to the inlet port 22 of the rotary pump. As the pump picks up speed, the restriction in the inlet conduit I9 causes the formation of a considerable vacuum which is transmitted through the duct 6I to the sealed chamber 66. To build up the pressure of the b y-passed fluid, the passage 53 is here made small and restricted and thus sufficiently resists the building up of pressure. This the underneath side of the valve member 44 tending to raise the valve in opposition to the spring 49. Accordingly, when the pump speed has been built up to a certain amount, the vacuum and the pressure become suiliciently great to overcome the force of the spring 49 and consequently the sleeve valve member 44 is drawn upwardly shutting oif communipressure acts on cation from the conduit 40 to the annular chamber 46. This position is most clearly shown in Fig. 4. When the passage 4D is closed, the annular chamber 34 becomes a dead-end and the full speed pump pressure immediately builds up a huid force in the annular chamber suicient to snap the lower diaphragm 35 downwardly. The movement of the diaphragm downwardly carries with it the disk valve 36 thereby uncovering an outlet port 62 and an auxiliary by-pass port 63. The outlet port communicates with a conduit or passage 64 which leads outwardly to the threaded outlet 65 to which a' nozzle may be connected. The diaphragm 35 is suitably apertured where the passage 64 intersects the same. A bleed conduit 66 connects the auxiliary bypass port 63 with the annular chamber 46 on the upper side of the valve body from which there is a direct communication through the conduit 53 and the chamber 54 to the intake side of the pump. By means of the bleed conduit 66, a pressure is maintained in chamber 46 to aid the vacuum in maintaining the main by-pass closed. It is believed apparent that, while both suction and pressure are here employed, either might be employed alone by a proper adjustment be further observed of the tension of the spring 49 and the extent of restriction in the passage I9 or the passage 53.V Use is again made of a ball seal consisting of a ball 64 positioned to seal the passage 64 laterally from the outside after it is initially drilled during the course of manufacture.

It will be observed from the foregoing that, when the pump has reached the proper speed, there will be a closing of the normally open bypass followed by a sudden opening of the discharge passage leading to the nozzle. It will that, since the size of the opening leading to the nozzle is somewhat larger than the size of the bleed conduit leading to the valve device, ui'd in quantity will be first fed to the nozzle. However, because of the fact that the capacity of passage 64 is nsuflicient to conduct all of the fluid pump, a surplus of fluid will be presentand that will be sent somewhat axially through the smaller bleed conduit back through a part of the normal by-pass system to the pump inlet. By this arrangement the operation of the pump is cushioned and a smooth vibrationless operation is assured at all times.

As soon as the power is shut off and the pump ceases operation, thesuction lset up by the restriction 20 in the intake conduit I9 will be immediately reduced to a negligible quantity and the pressure in chamber 46 will also be reduced. The reduction in suction being transmitted immediately to the chamber underneath the cap 8 will reduce the suction above the upper diaphragm and the tension in the spring 49 will then immediately be suiiicient to push the sleeve valve downward to open the normally acting by-pass. As soon as the by-pass is opened, communication from the annular chamber 34 back to the pump intake will be immediately reestablished and the pressure against the lower diaphragm will be released. The release therefore of pressure against the lower diaphragm will be effective to permit the disk valve 35 to snap back into place under strong spring tension, abruptly closing the outlet port and auxiliary by-pass port and immediately stopping discharge to the nozzle before the pressure has been appreciably reduced. There will accordingly be produced a quick shutoff of fluid at the nozzle while the pressure of the fluid is at its maximum.

Normally the lower diaphragm 34 is held upwardly in a closed position by a heavy helical spring 61 which has at its inner end a washer 68 having a concentric semi-spherical knob or button 69 bearing pivotally against the cupshaped chamber 31. At the lower or outer end the helical spring 61 has a second washer 1l! having a semi-spherical depression 1I at the center in which the correspondingly shaped end of a screw 12 is inserted. A cap 13 iits over the bottom end of the screw 12 and acts as a locking and sealing device after the screw 12 has been turned in or out to adjust the spring pressure against the lower diaphragm 35. A threaded aperture 14 supplies a connection for a gauge and communicates by means of a passage 15 through a suitable aperture at the edge of the diaphragm, with the annular chamber 34 and consequently -is always responsive to the discharge pressure from the pump. A vent passage 11 relieves any tendency toward an air cushion behind the lower diaphragm. i

At the left of the pump base there is a rotating seal 16 which may be of a type illustrated by Patent No. 2,015,979, but which does not form a part of this invention. The

purpose of a seal layed action of the valve controlling the dis'- charge performs a double function. When the current is turned on to start the pump, a fan of the usual sort, connected to the burner box, is simultaneously started. No volume of air which the fan is capable of injecting into the' burner box is immediately sulcient to supply oxygen for complete combustion of fuel which might be injected. Consequently, when a device as described herein delays the injection of fuel into the iireborr, there will have been previously introduced a sucient volume of air to effect complete and eificient combustion when fuel oi] is finally injected, at the nozzle, at its maximum pressure. A similar economy is effected when the fan and motor are shut off. Since at this stage the volume of air being forced into the burner box drops oif immediately upon a slowing up of the fan, there would be insufiicient air to burn completely fuel oil which would continue to be injected due to an otherwise gradual slowing up of the pump. In the appa-I ratus herein described, as soon as the fan is cut off, the supply of fuel is likewise instantaneously cut off and no partial or incomplete combustion is allowed to take place.

There has thus been provided a novel and eflicient pump and uid control means which operates instantaneously at full pressure and at a p roper time, and which cuts off the iiuid supply at practically full pressure as 'soon as the demand for it ceases. 'Ihe device is adjustable tovarous pump capacities and discharge pressures and supplies a mechanism suited to an infinite variety of circumstances.

I claim as my invention:

1. A uid pressure generating and control mechanism comprising, in combination, a base,.

a housing secured to said base and having an inlet for connection to a source of iiuid, a pump mounted on said base having an intake port communicating with the interior of said housing and a discharge port, said pump being operable to generate suction at the intake port and pressure at the discharge port, a screen in said hous ing interposed between the intake of the housing and the intake of the pump and a delayed actuation valve mechanism disposed in said housing and controlling the discharge from said pump comprising a valve body having 'a recess in one face thereof forming part of a chamber communicatng with the discharge port of the pump, a

flexible diaphragm clamped between said valve body'and an annular shoulder in said housing completing said chamber, a valve seat in said.

chamber having a main discharge passage opening therethrough, avalve element carried by said flexible diaphragm so. as to be responsive to the pressure in the chamber controlling said main discharge passage, meansfor urging said valve element normally toengage said seat and prevent discharge through said main passage, a recess formed in the opposite face of said valve body to constitute part-of a second chamber, a duct leading from said first chamber tosaid v second chamber, an' annular exible diaphragm,

a. cap securing the outer periphery of said annular diaphragm between said cap and said valve a movable valve element clamped to the inner periphery of said annular diaphragm and l with said rst chamber to prevent the building up of pressure within the rst chamber sumcient to open the valve disposed therein, and a conduit for communicating the suction at the intake of said pump to the interior of said cap for actuating said movable valve element to close said duct when the suction reaches a predetermined value.

2. A fluid control system comprising a strainer cup, a pump feeding therefrom having an inlet passage and a restricting means in the inlet passage for initiating suction when the pump is in operation, means forming an outlet conduit from the pump, a delay valve mechanism in the outlet conduit comprising a first valve member havond conduit of smaller capacity communicating between the valve seat and the pump inlet for releasing surplus iiuid; a second valve member having a body portion shaped to form a second chamber, means forming a conduit to the rst vvalve member from the second chamber, a diaphragm forming one wall of the second chamber, and a sleeve valve mounted thereon having a cylindrical seat within the second chamberoperable to open and close said conduit, means forming a by-pass from the second valve chamber to the pump inlet, means forming a sealed chamber on the outside of said second valve diaphragm enclosing a spring for normally depressing said diaphragm to a position for opening said sleeve valve, and means forming a duct leading from the sealed chamber to the pump inlet on the pump side of the restricting means for admitting'suction to the diaphragm when the pump is in operation the suction being effective to draw the diaphragm and sleeve valve to a closed position, thereby forming a closed compression chamber within the delay valve mechanism immediately subject. to pump pressure and operable to move the first valve element against its spring to an open -position to allow direct discharge of the iluid.

3. A fluid control system comprising a source of fluid. supply, a pump having an inlet and a restricting means in the inlet for producing suction when the pump is operated, means forming an outlet conduit from the pump, a delay valve `mechanism in the outlet conduit comprising a valve member having a body forming a chamber always in communication with said conduit and means forming a pocket adjacent the chamber, said chamber having a movable wall including a, ow restricting valve element mounted thereon, a valve seat in the chamber and resilient means supported in the pocket in contact with the movable wall for normally holding the wall and valve element in a positionfor seating the valve element against the valve seat, means forming a rst Il conduit communicating with the valve seat for discharge of uid, means forming a second conduit communicating between the valve seat and the pump inlet for releasing surplus fluid, and means forming a return conduit from lthe valve mechanism having a valve device therein for opening and closing the return conduit and a passage from the valve device to the source of supply, said valve device having a chamber provided with a movable partition supporting one element of the valve device, means forming a sealed space on the outside of the movable partition enclosing a resilient means for normally depressing the partition and the supported element to a position for opening said valve device, means forming a communication between the sealed space and the -pump inlet on the pump side of the restricting means for admitting suction to the diaphragm when the pump is in operation, said suction being effective to draw the supported element of the device to a closed position, forming a closed compression chamber in the delay valve mechanism immediately subject to pump pressure and said pump pressure being operable to move the flovv restricting valve element against its resilient closing means to an open position to allow direct discharge of the fluid from the valve mechanism simultaneously with a release of surplus fluid.

4. A uid control system includinga source of fluid comprising a pump having an inlet and a restricting means therein for producing suction and an outlet for discharging fluid under pressure, means forming an outlet conduit from the pump, a delay valve mechanism in the outlet conduit comprising a body forming a chamber al-- ways in communication with said conduit, a valve seat in the chamber and a spring pr`e`s'sed valve element movable against the seat for normally closing the valve mechanism, means forming a first conduit communicating with the valve seat for the discharge of fluid, and means forming a second conduit in communication between the valve seat and the source of fluid for releasing surplus fluid, a second valve mechanism having a body including a chamber, and means forming a passage from the second valve mechanism to the delay .valve mechanism, having therein a valve element for opening and closing said passage forming part of the second valve mechanism and yieldably retained in a normally open position, means forming a return passage from the second valve mechanism to the pump inlet, casing means forming a sealed space on the outside of the last named valve element, and means forming a communication therefrom to the pump pump side ofthe restricting means the last named valve said inlet on the for conducting suction to element when the pump is in operation,

suction being effective within the sealed space to draw the yieldable valve element to a closed posiu tion, thereby shutting oi the return passage and forming a closed compression chamber in the delay valve mechanism subject to pump discharge pressure, said pressure being operable to move the first named spring pressed valve element to open position to allow direct discharge of the iiuid and a simultaneous release of surplus uid.

5. In a control mechanism for a fluid system including a source of supply and a pump having an inlet conduit with means therein for creating a suction and a discharge conduit, the combination of a delay valve device for normally closing the discharge conduit and a second valve vdevice comprising a chamber, one wall of said chamber ved on s aid element, means .oi supply for ilud and means thereby f the movable wall, and means and a valve mountforming a conduit from the chamber to the source of supply, means forming a normally open by-pass from the chamber to the delay valve device, said by-pass being controlled by said second valve device, a normally closed by-pass from the delay valve device to the pump, ableto close the normally open by-pass when the pump is in operatic and means subject to pump pressure to open the normally closed bypass and to simultaneously open the discharge conduit from the pump.

6. A fluid control system including a source for generating uid pressure, means forming a discharge .conduit from said generating means, a delay valve device in the conduit comprising a chamber having a valve seat, a movable wall and a valve carried by the wall, means forming an open passage from the chamber to the source of supply, said valve device having a cover member over the outside of the movable wall forming a closed compartment and a vent from the compartment to the source of fluid supply, there being an adjustable resilient means in the compartment positioned against the movable wall, said valve seat being normally closed by the valve carried by forming a discharge outlet together with means forming a by-pass outlet from the valve seat to the source of supply simultaneously operable by the valve when the fluid pressure is sufficient to open said valve against the adjustable resilient means.

'7. A fluid control system including a source of supply for uid and means for generating fluid pressure, means forming a discharge conduit from said generating means, a delay valve device in the conduit comprising a chamber having a valve seat and a valve member movable with one wall thereof, said valve device having a cover member adjacent the valve member forming a closed compartment and a vent from the compartment to the source of fluid supply, resilient means in the compartment operable normally to press the valve member against the valve seat to close it, and means forming a direct discharge outlet together with means forming a by-pass outlet from the valve seat to the source of supply, jointly operable by the valve member when the uid pressure is sufficient to open said valve member against the resilient means. Y

8. In a uid system including a source of `supply and a pump, having inlet and discharge passages thereto, a control mechanism for minimizing disturbances in the pump comprising a valve device for attachment in the discharge passage from the pump including a valve having its outlet port in interrupted communication with the discharge passage, and means in the device for holding the valve normally in a yieldably closed position for shutting off the ow of fluid from said passage, said valve device having also a by-pass systemfor normally connecting the discharge passage with the source of supply comprising means forming an open primary by-pass having capacity sufficient to accommodate the entire pumpv discharge at speeds below full speed, and means forming a secondary by-pass having capacity sufcient to accommodate a portion only of the pump discharge at full speed, said secondary by-passhaving an entrance thereto positioned adjacent the normally closed valve, a valve member in the primary by-pass, and means for automatically closing said primary by-pass when including a movable element means subject to pump suction opercomprising a valve element, an outlet positioned' for communication with the discharge line and means for holding said valve element in a yieldably closed position for shutting off the flow of uid from the discharge line to the outlet, means forming a primary normally open by-pass from the valve mechanism having capacity sumcient to accommodate the entire pump discharge at speeds below full speed and valve means in the by-pass in communication with the pump and automatically operable to close said by-pass'when the pump reaches full speed, and means forming a secondary by-pass having a capacity sumcient to accommodate a portion only of the pump discharge at full speed and having an entrance thereto positioned adjacent the valve element, said valve element being subject to discharge pressure from the pump and operable thereby to simultaneously open the discharge line and the secondary by-pass upon closing of the primary by-pass.

GUNNAR A. WAHLMARK. 

